1. Field of the Invention
The present invention generally relates to planar antennas. More specifically, the present invention relates to a dipole microstrip antenna for use in wideband applications, which provides a wider operating bandwidth and capability in Ultrahigh Frequency (UHF) and Superhigh Frequency (SHF) bands.
2. Related Art
Wireless communication devices are now becoming commonplace in the electronics industry. Wireless networking of portable computers and associated devices is now replacing a large segment of the networking market. Wireless communication devices, including wireless networking adapters, hubs and other equipment, utilize radio transmitters and receivers to transmit data signals from one device or node to another. These radio transmitters and receivers have to utilize a specific frequency band and protocol to accomplish this task. Since these wireless networks and communications areas may often overlap, standards, protocols and privacy protection are necessary. One current standard in the industry has been established by the Institute of Electrical and Electronics Engineers, Inc. (IEEE) and is known as IEEE 802.11. It is a family of specifications for wireless local area networks (WLANs). There are currently four specifications in the family: 802.11, 802.11a, 802.11b, and 802.11g, all operating in the 2.4 GHz band, except for 802.11a, which operates in the 5 GHz band.
Another standard in wireless communications and networking is known as Bluetooth and is being established by a collaborative group of communications and computer companies. Devices incorporating Bluetooth technology can utilize a micro-chip transceiver for communication between devices. Bluetooth technology promises to be a viable and economical networking solution for interconnection of cell phones, computers, printers, modems, computer peripherals, fax machines and other communications and computing devices. The size of the Bluetooth transceiver can make it usable in devices as small as palmtop computers and cell phones.
Antennas are well known for enabling and improving transmission from radio transmitters and to radio receivers. Antennas can dramatically increase the range of radio transceivers. However, most antenna designs function best when protruding from their host device. In small electronic devices, protruding antennas are often vulnerable to breakage as the devices are often stowed in purses, pockets, backpacks and other areas where damage can occur.
Known microstrip antennas made of metal traces are lightweight, low profile, low cost devices suitable for replacing many of the more bulky antennas. Conventional microstrip antennas have an inherently narrow frequency bandwidth that limits more widespread usage. Numerous attempts to increase this bandwidth have attained little success. For example, U.S. Pat. No. 4,737,797, entitled xe2x80x9cMicrostrip Balun-Antenna Apparatusxe2x80x9d discloses a balun planar antenna. The planar antenna apparatus includes a butterfly microstrip antenna printed on one side of a substrate and a balun input strip transmission line printed on two sides of the substrate using a conventional printed circuit process. The transmission line is coupled to the butterfly microstrip antenna via a balancing section. The operating center frequency of this antenna is 1.7 GHz and the bandwidth is 400 MHz. A length of a rectangular loop of the balancing section is 1.7 cm. If the additional length of the balun input strip transmission line is taken into account, the size of the antenna is still too large for a small communications transceiver, such as a mobile telephone.
Previous wide-band antennas, such as the horn, helix and log periodical antennas, all suffer from being bulky, heavy and nonconformal. Therefore, it is desired to combine the best characteristics of the microstrip and wideband antennas into one antenna.
It is an object of the present invention to provide a microstrip antenna structure which has a small antenna length, is high in efficiency and is usable over a wide band in multi-frequency ranges.
To achieve the above objects, a microstrip antenna structure in accordance with a preferred embodiment of the present invention includes a dipole antenna comprising two dipole elements spaced apart from each other, a dielectric substrate on which the dipole elements are symmetrically disposed, and a feeding system connected with the dipole antenna. Each dipole element comprises a triangular patch and a tentacle patch extending therefrom. The two dipole elements are mounted together to form a butterfly structure antenna. The butterfly structure provides the dipole antenna with an excellent broadband range at multiple frequencies.
These and additional objects, features and advantages of the present invention will become apparent after reading the following detailed description of a preferred embodiment of the invention taken in conjunction with the appended drawings.